1. Field of the Invention
The present invention pertains to moisture absorbing materials. More specifically, the present invention pertains to moisture absorbing materials made from rice hulls.
2. Description of the Prior Art
There are many environmental situations in which too much water or other liquids are present. To remedy such, various means are used to reduce the presence of excessive liquids. If a large amount of liquid accumulates at one location, it may be pumped, bailed or otherwise transferred to some other location. In other situations, drying must occur by simply depending on time consuming natural environmental drying processes. To speed up drying or absorption of liquids, a number of desiccant or drying agents may be used. For example, calcium chloride is a commonly used desiccant. However, some desiccants have various undesirable characteristics. They may be relatively expensive. They may be severely limited in absorbing capacity. They may not be easy to remove after absorbing capacity is exhausted. Such desiccants may not be practical for recycling, i.e. capable of reclaiming the liquids absorbed thereby.
There are other situations in which retention of fluids is desired. For example, in the soil of dry and arid environments, it may be desirable to collect water when available and hold the water for subsequent gradual release. If not properly collected and retained, the water may quickly evaporate and not be available for absorption by the roots of plants in the soil.
A variety of materials have been used as desiccants or moisture absorbing agents. One such material is rice hulls. Since rice hulls have been generally regarded as a waste product of preparation of rice grains, they are readily available and inexpensive. In U.S. Pat. No. 4,407,789, rice hulls, ground into fine particles are used as a component of body powder to provide moisture absorption capabilities, it being asserted that such unburned rice hulls absorb 16% moisture by weight. In U.S. Pat. No. 4,619,911, burned rice hull ash is a component of lightweight silicate aggregate which can be used as an absorbent of improved characteristics or as a filler for concrete. However, to produce the desired results, the rice hull ash must be mixed with an alkali metal hydroxide, boric acid and water, heated to approximately 160.degree. F. and cured. After crushing and grinding into discrete particles, the composition must be heated and expanded in a furnace at temperatures of between 800.degree. F. and 1000.degree. F. However, such a material would be toxic and unsafe for use in soils for edible plant production.
Pure, cheap, easy to produce and easy to use liquid absorbing materials are needed for a variety of uses. Such materials which collect and retain liquids, such as water, for gradual future use are especially needed for agricultural uses.